The transmigration of the soul. It really is a beautiful metaphor for describing the mysterious process of death. If the idea of the past possessing the present is intuitive (indeed it becomes more so every day), then the idea that past spirits are reestablised in new bodies or forms really isn't that far of a strech. Now keeping in mind that, as Dr. Sexson said, this concept is one big metaphor, I wonder if the ancient cultures of the world where metempsychosis origninated held a similar view of its metaphorical use. I quickly googled the word and came upon a website which listed the various forms of metempsychosis and the several cultures which established their own variation into their belief systems.
Beginning with the Egyptions and proceeding in chronological order, the website I found gave a brief history of all known cultures to employ the ideas of transmigration. I found it very interesting that this idea of reincarnation was such a common explanation of the intimidating process of dying, spanning cultures, time periods, and continents. Although the basic idea of metempsychosis was the common link between ancient Egypt, Greece, and India, the details of the transmigration belief were very different. Brahmanism, which originated in India, proclaimed a system of what seems to be everlasting karma. Wrong-doings committed in a current life time were believed to follow that soul into the next life or even several lifetimes down the road. It was understood that negative events could be a punishment for an act committed centuries in the past.
It's funny, reading all these classical texts and learning about the beliefs of reincarnation and soul migration and mystical happenings, it all seems like a fairy tale. Our perspective as twenty first century humans would have us believe that these stories are idealistic fables used simply to entertain. However, when you think about it, these stories are no more idealistic than the tales of the relgions which drive a majority of the modern world. The answers relgion seeks to provide are no more concrete today than they were hundreds, thousands, or millions of years ago. The same exact questions remain and as long as human consciousness exists, there will be no answers.